Low-oil content high-tension oil circuit breaker



Dec. 29, 1959 A. GANTENBEIN LOW-OIL CONTENTHIGH-TENSION OIL CIRCUITBREAKER Filed Jan. 22, 1957 2 Sheets-Sheet 1 7 Am N J f M/l/E/V 70AANDREAS GANTE/VBfi/V by i!!! A fame A fl n 8 6 m U u a, 3 a 1 x r//////V A w United States Patent Ofifice 2,919,330 Patented Dec. 29,1959 LOW-OIL CONTENT HIGH-TENSION OIL CIRCUIT BREAKER AndreasGantenbein, Zurich, Switzerland, assignor to Oerlikon EngineeringCompany, Zurich, Switzerland, a corporation of Switzerland ApplicationJanuary 22, .1957, Serial No. 635,427

2 Claims. (Cl."200-:-150) This invention relates to a low oil contentcircuitbreaker of the kind in which oil is injected into the arc controlchamber.

In circuit breakers of this type a known arrangement is to provide apump inside the insulator for injecting oil into the arc control chamberthrough a tubular movable contact finger when the circuit is ruptured.However, this arrangement permits only a comparatively small amount ofoil to be injected into the arc control chamher since the circuitbreaker insulator offers insuflicient space for anything but a smallpump, the effect of which when the circuit is broken is correspondinglysmall.

In the present invention provision is made for the injection of alargerquantity of oil into the are control chamber. To this end the inventionprovides .an oil pump on the pedestal of .the circuit breaker for thepurpose of forcing .oil through a hollow supporting insulator into thearc control chamber which is fitted with a non-return valve that permitsoil to .enter the arc control chamber only at pressures below apredetermined magnitude corresponding to the pressure engendered by therupturing of a current-of comparatively low value.

The size of the oil pump is therefore not determined by theavailablespace on the inside of the circuit breaker butmaybe dimensionedto suit a delivery volume commensurate with what is required for thereliable suppression of the arc. ,Moreover, a pump so disposed .offersthe further advantage of being more accessible to inspection and easiertomountin. position than a pump inside the circuit breaker.

The oil pump may be connected with an oil accumulator which fills thepump independently of the amount of oil available in the arc controlchamber, with the resultant advantage that the .pump retains itsarc-controlling efiect even when the. circuit ,is .broken repeatedly inrapid succession, the,pump always injecting an adequate supply of oilinto .the .arcicontrol chamber to extinguish the are. This is .a matterof'especial importance in the case of circuit breakers which are usedfor short interruption, that is to say for breaking the circuit .forshort periods of time and then closing the circuit again, an actionwhich may be repeated a number of times before the circuit ispermanently ruptured should the cause of the fault persist.

In order 'to enable the invention to .be more readily understood,referencei-s .madeto the accompanying drawings which illustratediagrammatically and by way of example, one embodiment thereof and inwhich:

Fig, 1 is a longitudinal section of an arc control chamber; and

Fig. 2"is a longitudinal section on a smaller scale of one electroderofthecircuitbreakr and of the associated pump.

As shown :in .Fig. .1 .an .arc control chamber 1 -is arranged inside theupper insulator 2, the top 3 of the circuit breaker being securedthereto. The are control chamber is arranged for cross-jet arc controland forms an integral unit with the gas venting channel 5 whichdischarges into the separator tank 4. The are control chamber 1 consistsessentially of two tubular members 6 and 7 made of a plastic and a glassfibre fabric. The inner cylinder 6 encloses the space in which arcingoccurs, while the space between cylinders 6 and 7 serves as an adjacentventing channel 5. The outer tubular member 7 is suspended by means of aring 8 from the top 3 of the circuit breaker and is covered with a plate9 which carries a fixed contact 10 and is provided with an opening 11for the gas venting channel 5. The bottom of the tubular member 7 isclosed by a plate 12 provided with an opening 13 for a valve 14, anopening for the movable contact finger 16, and a return flow opening'17. The inner tubular member 6 contains the fixed contact 10 with thecontact fingers 18 and an arcing piece 19. The tubular member 6 enclosesthe actual spark gap 20 which communicates through four trans verseslots 21 with the gas venting channel 5 and through valve 14 with thecavity enclosed by the insulator 2. A resistor 22 disposed between thetubular members 6 and 7 connects plates 9 and 12 and thereby forms abridge across the arc control chamber 1.

The upper part 3 vof the circuit breaker is partly filled with oil 23the space above the oil level serving as a separating chamber 4 for thecollection of the oil. A cover 24 with a breather opening 25 and an oilbafile 26 forms the cap ,of the top part 3 of the circuit breaker. Aconnector 27 is electrically connected with contact 10 through ring 8and plate 9.

Fig. 2 shows one of the electrodes in the open position, the arc controlchamber 1, the insulator 2 and the top portion 3 thereof. 28 is ,ahollow supporting insulator through which an oil pump 30 arranged on thepedestal 29 can force oil into the arc control chamber 1. 31 is ,aflange with roller-type contacts 32 and openings 33. The roller contacts32 establish the electric connection between the movable contact finger16 and a stud connector 34. The movable contact finger 16 is operatedthrough a shaft 35 by means of a lever 36, a shackle 37, and aninsulating rod 38. For the purpose of its operation the contact fingeris controlled by an interrupter spring 39 which acts on a lever 40.Through shackles 41 lever 49 operates a piston rod 42 with a head member43, a slidable piston 44, and a spring 45 which together constitutes theoil pump 30. The latter also comprises a cylinder 46 which encloses theslidable piston 44. Adjacent to the pump cylinder 46, at a low part ofthe oil circulating system, is an accumulator consisting of inner andouter chambers 55 .and.46a. The piston 44 has a fixed stroke extendingfrom the forward position of'the piston, shown in full lines, to therearward position shown in dotted lines. The spring 45 constantly urgesthe piston 44 forwardly toward the end of the cylinder :whichcommunicates with the hollow insulator 28. In this end of the cylinderthere are non-return valves 47 allowing oil flow from the pump to theinsulator 28. When the contact 16 is moved upwardly to close the circuitat 13, 19, the enlargement 43 on the piston rod 42 pulls the pistonrearwards to the dotted position against the urgence of the spring 45.When the contacts 16 and 18 are separated the piston is released forforward movement by the spring 45.

Between the pump cylinder 46 and the oil accumulator there are parallelcommunications 53 and 54 which establish a loop circuit through whichthe oil flows from the rear to the front ofthe piston 44 whenever thepiston moves rearwardly. Non-return valves -48 are arranged in thisloop.

At its lower end, the inner accumulator chamber 55 is provided withnon-return valves 49 through which make-up oil is withdrawn when thepiston moves forwardly.

Oil is pushed through valve 14 into the arc control chamber 1 wheneverthe pressure differential on the outside and inside of the chamber is ofpredetermined magnitude. This occurs when the ruptured current isrelatively small. A stream of oil is always available under thesecircumstances to move transversely across the arc in the chamber 1 toextinguish it. The oil and gases generated move through the slots 21into the gas venting channel 5. The oil ultimately returns by gravity tothe circulating system through the return flow opening 17, thence backto the accumulator through return flow openings 50, 51 and 52.

When the circuit breaker is to be closed, an actuating device (not shownin the drawing) deflects levers 36, 40 on shaft 35 in thecounterclockwise direction until the movable contact finger 16 touchesthe fixed contact finger 18 (Fig. 1). In the closed position of thecontacts both the interruptor spring 39 as well as the oil pump spring45 will have been stressed or energised and the piston 44 will be in therearward position indicated by the dotted lines. The downward movementof the piston 44 forces oil out of the space in the cylinder below thepiston 44 through channel 54, valves 48, and channel 53, back into thepump cylinder 46 above the piston 44. During its downward travel theskirt of the piston 44 gradually closes channel 54 thus creating asmaller and smaller opening through which oil from below the piston 44can still escape. Thus the piston during its rearward movement willserve as a damping element when the contacts are closed.

If the current when the contact fingers 16, 19 separate (Fig. 1) isrelatively small, then only a low energy are 56 will be formed whichwill dissociate only a small volume of oil and cause a comparativelysmall flow through the slots 21 owing to the relatively limited increaseof the pressure in the arc control chamber 1. The oil pump 30 (Fig. 2)will therefore pump oil in the direction indicated by the arrows throughthe hollow supporting insulator 28, the openings 33, and the opennon-return valve 13, 14 (Fig. 1) into the spark gap 20 where the oilwill cross the are 56 and quench it, and then escape through the gasventing channel 5 into the separator chamber 4.

Also, when the circuit breaker is opened, oil flows out of chamber 55through the non-return valves 49 and through channel 54 into the spacechamber below the pump piston 44. If the circuit breaker remainsinoperative after rupture, the oil forced by the pump into the arccontrol chamber 1 can gradually flow back from the separator chamber 4into the accumulator 55. To this end the lower cover plate 12 (Fig. l)of the arc control chamber 1 is provided with the return flow opening 17and further openings 50, 51, 52 are provided as previously described(Fig. 2).

If the circuit is reclosed and then interrupted a second time shortlyafter having been broken for the first time, then there will be no timefor the oil to return to the accumulator 55, so that the pump must againwithdraw the required oil from the accumulator 55. The capacity of thelatter is therefore so determined that it will permit the circuitbreaker to interrupt several times in succession, as is sometimesrequired of short time circuit breakers.

If, on the other hand, a heavy current, such as a shortcircuit current,is interrupted, then the are 56 forming between contacts 16 and 19 willdissociate sufficient oil for the gases thus evolved to generate a highpressure in the spark gap 20 (Fig. 1) and without the assistance of thepump 30 there will be created a powerful cross blast through the slots21, which will rupture the are 56. Owing to the high pressure generatedin the spark gap 20 the nonreturn valve 14 will close and prevent thepump 30 from forcing oil into the arc control chamber 1 so that thepiston 44 will remain stationary. Nevertheless the breaker movement willcontinue under the action of the interruptor spring 39, because thepiston rod 42 can slide in the stationary piston 44 and allow lever 40,shaft 35, lever 36, shackles 37, and insulating rod 38 to participate inthe movement of the movable contact finger 16.

What we claim is:

1. In a high-tension circuit breaker, a pair of relatively movablecontacts adapted to be moved together to close a circuit and separatedto break it, an arc control chamber enclosing a space in which arcingoccurs, a hollow insulator supporting and enclosing said chamber andfilled with oil which immerses said chamber, a wall of said chamberhaving a non-return valve to admit oil into the chamber when thepressure ditferential on the outside and inside of the chamber is ofpredetermined magnitude, an oil circulating system including a pumpcylinder having one end in communication with said insulator, a pistonmovable forwardly toward said end and rearwardly away from it, a springconstantly urging the piston forwardly, a mechanism for moving saidcontacts, and means operated by said mechanism for moving and retainingsaid piston rearwards when the contacts are moved together and forreleasing said piston when the contacts are separated, an oilaccumulator in a low part of said circulating system, parallelcommunications between said accumulator and pump cylinder to establish aloop circuit in which the oil flows from the rear to the front of thepiston whenever the piston moves rearwardly, and a non-return valvearranged in said loop, said accumulator comprising outer and innerchambers, the inner chamber having a non-return valve at its lower endfrom which oil is withdrawn when the piston moves forwardly.

2. A high-tension circuit breaker comprising a pair of relativelymovable contacts adapted to be moved together to close a circuit andseparated to break it, an are control chamber enclosing the space inwhich arcing occurs and including a gas-venting channel alongside saidspace, a hollow insulator supporting and enclosing said are controlchamber and filled with oil which immerses said chamber, a wall of saidarc control chamber having slots leading to said gas-venting channel andso located that an arc-quenching stream of oil moving transverselyacross an arc will pass through said slots into said venting channel,said chamber being also provided with an oil inlet in a wall thereof, anoil circulating system including a pump in communication with saidhollow insulator and adapted to push oil through said inlet into saidchamber, a nonreturn valve in said inlet adapted to open to admit oilonly when the pressure within said chamber is below a predeterminedmagnitude, said venting channel having an opening through which oil mayreturn by gravity into said insulator, said oil system including an oilaccumulator located at a low part of said system, and means for feedingmake-up oil from said accumulator to said pump whenever oil has enteredsaid are control chamber, whereby the oil supply to be acted upon by thepump is maintained irrespective of said return of oil from the ventingchannel.

References Cited in the file of this patent UNITED STATES PATENTS819.524 Delany May 1, 1906 2,258,226 Skeats Oct. 7, 1941 2,281,385 St.Germain et al Apr. 28, 1942 2,650,972 Kuwayarna Sept. 1, 1953 2,668,217Vogelsanger et al. Feb. 2, 1954 2,749,412 McBride et al. June 5, 1956FOREIGN PATENTS 499.663 Great Britain Jan. 26, 1939 500,731 GreatBritain Feb. 13, 1939 374,500 Italy Aug. 26, 1939 716,296 Germany Jan.16, 1942 ,Mwiunmmrlilllmut t

